Top-ranked Rafael Nadal will be working to increase grip atop the rankings at the ATP Toronto Masters, an event which lost an exhausted Andy Murray prior to Monday's start.

Rafael Nadal (AP Photo)

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Top-ranked Rafael Nadal will be working to increase grip atop the rankings at the ATP Toronto Masters, an event which lost an exhausted Andy Murray prior to Monday's start.

Britain's Murray, winner of three matches in four days this week in Washington, withdrew from Washington and Canada on Friday after finishing his latest victory after 3 a.m., breaking down in tears after the match.

But the cumulative effort was too much for the 31-year-old Scotsman, who underwent right hip surgery in January.

"I'm exhausted after playing so much over the past four days, having not competed on the hard courts for 18 months," Murray said.

"I also need to be careful and to listen to my body as I come back from a long-term injury."

The former number one, now ranked 832, was playing the third event in his slow-running comeback after first returning in June on grass in Britain before withdrawing from Wimbledon.

World number two Roger Federer is skipping Canada and will return on August 13 in Cincinnati, where Murray is also expected.

Federer, limiting his schedule to extend his longevity, turns 37 on Wednesday.

Nadal will be making his first appearance on court since a five-set Wimbledon semi-final loss to Novak Djokovic.

With most of the rankings top 10 in Canada, Nadal's path to a potential fourth title in the country after 2005, 2008 and 2013 will be a predictable challenge.

The Spaniard resumed training recently on his home island of Mallorca after spending off-time sailing.

Nadal opens play on Wednesday against either American Jared Donaldson or Frenchman Benoit Paire, fined $16,500 this week for a racquet-smashing outburst in Washington.